The present applicant has heretofore proposed a position sensor which optically senses a pressed position with the use of an optical waveguide (see PTL 1, for example). As shown in FIG. 17A, this position sensor includes a rectangular sheet-like optical waveguide W10 configured such that a sheet-like core pattern member is held between a rectangular sheet-like under cladding layer 11 and a rectangular sheet-like over cladding layer 13. The aforementioned core pattern member includes: a lattice-shaped portion 12A including a plurality of linear cores 12 serving as an optical path and arranged vertically and horizontally; a first outer peripheral core portion 12B disposed along a first horizontal side and a first vertical side of the outer periphery of the lattice-shaped portion 12A; and a second outer peripheral core portion 12C disposed along a second horizontal side and a second vertical side which are opposed to the first horizontal side and the first vertical side, with the lattice-shaped portion 12A therebetween. The first outer peripheral core portion 12B includes a single core 26. The vertical and horizontal cores 12 of the lattice-shaped portion 12A have respective front ends branching off from the single core 26. The second outer peripheral core portion 12C includes cores 27 extending from the rear ends of the respective cores 12 of the lattice-shaped portion 12A. In the position sensor, a light-emitting element 14 is connected to an end surface of the first outer peripheral core portion 12B of the core pattern member, and a light-receiving element 15 is connected to an end surface of the second outer peripheral core portion 12C thereof.
In the position sensor including such an optical waveguide, light emitted from the light-emitting element 14 branches from the core 26 of the first outer peripheral core portion 12B into the cores 12 of the lattice-shaped portion 12A, passes through the cores 27 of the second outer peripheral core portion 12C, and is received by the light-receiving element 15. A surface portion (a rectangular portion indicated by dash-and-dot lines in the center of FIG. 17A) of the over cladding layer 13 corresponding to the lattice-shaped portion 12A serves as an input region 13A for the position sensor.
Input to the position sensor is performed by pressing the input region 13A, for example, with a pen tip for input. This deforms at least one of the cores 12 which corresponds to the pressed part to decrease the amount of light propagating in the at least one core 12. The intensity of light received by the light-receiving element 15 is accordingly decreased in the at least one core 12 corresponding to the pressed part. In this manner, the position sensor senses the pressed position. The position sensor is also capable of sensing the input of a character and the like through the use of the position sensing.
With the increase in the amount of transmission information, an optical circuit board in addition to an electrical circuit board has been employed in recent electronic devices and the like. An example of such electronic devices is shown in FIG. 18. In this electronic device, the aforementioned optical circuit board is stacked on the electrical circuit board. Specifically, the electrical circuit board 80 includes an insulative layer 81, and an electrical interconnect line 82 formed on the front surface of the insulative layer 81. The optical circuit board 70 includes an optical waveguide W20 (a first cladding layer 71, a core (optical path) 72, and a second cladding layer 73) stacked on the back surface (the surface opposite from the surface with the electrical interconnect line 82 formed thereon) of the insulative layer 81, and optical elements (a light-emitting element 74 and a light-receiving element 75) mounted on portions of the front surface (the surface with the electrical interconnect line 82 formed thereon) of the insulative layer 81 which correspond to opposite end portions of the optical waveguide W20 (see PTL 2, for example). In this optical circuit board 70, the opposite end portions of the optical waveguide W20 are formed into inclined surfaces inclined at 45 degrees with respect to the axial direction of the core 72. Portions of the core 72 positioned at the inclined surfaces function as light reflecting surfaces 72a and 72b. Portions of the insulative layer 81 corresponding to the light-emitting element 74 and the light-receiving element 75 have respective through holes 81a and 81b formed therein. The through holes 81a and 81b allow light L (indicated by dash-double-dot lines) to propagate (allow optical connection) therethrough between the light-emitting element 74 and the light reflecting surface 72a provided in a first end portion and between the light-receiving element 75 and the light reflecting surface 72b provided in a second end portion.
The propagation of light in the aforementioned optical circuit board 70 is performed in a manner to be described below. First, the light L emitted from the light-emitting element 74 passes through the through hole 81a of the insulative layer 81, and then passes through a first end portion (the right-hand end portion as seen in FIG. 18) of the first cladding layer 71. Then, the light L is reflected from the light reflecting surface 72a in a first end portion of the core 72 (or the optical path is changed by 90 degrees), and is propagated in the core 72. Then, the light L propagated in the core 72 is reflected from the light reflecting surface 72b in a second end portion (the left-hand end portion as seen in FIG. 18) of the core 72 (or the optical path is changed by 90 degrees), and passes through a second end portion of the first cladding layer 71 outwardly. Then, the light L passes through the through hole 81b of the insulative layer 81, and is thereafter received by the light-receiving element 75.
In some cases, an optical fiber is used in place of the light-receiving element 75 in a second end portion of the optical circuit board 70. In this case, the propagation of light is performed in the same manner as described above.